Light-sensitive photographic elements



o. w. MURRAY 2,462,534

LIGHT-SENSITIVE PHOTOGRAPHIC ELEMENT Feb. 22, 1949.

Filed March 29, 1946 INVENTOR.

OTIS WILLA RD MURRAY BY A TTORNEY RATIO CONTAINING CARBON PARTICLES.

Patented Feb. 22, 1949 LIGHT-SENSITIVE PHOTOGRAPHI C ELEMENTS OtisWillard Murray, Fords, N. J assignor to E. I. & Company, Wilmington,Delaware Application March 29, 1946, Serial No. 658,224

du Pont de Nemours Del, a corporation of 2 Claims.

This invention relates to novel photographic elements which have thephotosensitive layer or layers thereof protected from exposure tovisible light. More particularly it relates to such elements which areuseful for obtaining X-ray photographs or radiograms. Still moreparticularly it relates to X-ray films which can be safely handled underconditions of ordinary room illumination without exposure of thephotosensitive layers thereof and yield developed radiographs free fromcoloring matter.

Photographic elements with various types of antihalation layers havebeen proposed and manufactured commercially. In general they comprise asupport, a light-sensitive layer, and an antihalation layer composed ofa removable natural or synthetic material which has dispersedtherethrough an antihalation or light-absorbing dye or pigment. Thelight-sensitive layer is placed on one side of the base and theantihalation layer on the other. Various water-soluble cellulosederivatives and synthetic resins are among the substances which havebeen proposed. Materials which are soluble in dilute alcohol solutionsor in alkaline developer solutions have also been advocated but theyrequire special conditions for manufacturing or processing.

Photographic elements for obtaining X-ray photographs which are providedwith an opaque protecting medium for the sensitive layer are known. Theprevious protective layers, however, were not entirely satisfactory forX-ray films because the layers were diflicult to remove after exposureto X-rays and the light-blocking material is not uniformly distributedthroughout the layer.

Murray United States Patent No. 2,379,373 relates to photographicelements and, more particularly, to X-ray film elements comprising abase, a light-sensitive emulsion layer, a lightblocking outerantihalation layer disposed on each side of said element composed ofcasein and gelatin in the proportion of to parts of the former per partof the latter having intimately and uniformly dispersed therethroughfinely divided carbon particles. These elements, while commerciallypractical, sometimes have the disadvantage that complete removal of thefinely divided carbon is diflicult. A small amount of carbon particlessometimes becomes anchored to the photographic emulsion layer at thefusion point between the emulsion layer and the protective, layer.

This invention has for an object a photographic element for X-rays whichcan be handled under daylight conditions without exposure. A furtherobject is such an element which is provided with antihalation layerswhich can be removed easily and completely in aqueous baths. A stillfurther object is to provide such an element wherein the antihalationlayer is photographically inert and the light-blocking material isnon-diffusing and uniformly dispersed throughout the layers. A stillfurther object is to improve the photographic elements of the aforesaidUnited States patent.

The novel photographic elements or X-ray elements of this inventioncomprise a base having superposed thereon at least one photosensitiveemulsion layer, two outer light-absorbing protective layers disposed onthe outersurfaces of the elements, and a removable water-soluble colloidlayer intercalated between any emulsion layer and said protective layer.In the case of duplicoated X-ray film, the elements comprise a film baseor support having a photographic emulsion layer coated on each side ofthe base and a protective layer coated on each photographic emulsionlayer which contains a non-difiusing, lightabsorbing material.

The protective light-blocking or antihalation layers consist of anaqueous dispersion of a mixture of casein and gelatin and a black inertpigment such as colloidal carbon or finely divided' carbon black whichis uniformly distributed therethrough. The casein and gelatin arepresent in the amount of 10 to 20 parts of the former per part of thelatter. The amount of the black inert pigment particles may vary over afairly wide range but should be present in sufficient amount that thinlayers prevent visible light from penetrating therethrough and exposingthe photographic layers. A particle size of 10 to 100 mu represents apractical range and 30 to mu a preferred range for aforesaid pigments.

The coating mixtures can be made in the form of an aqueous dispersion orpaste and coated in a mannersimilar to that in which gelatin-silverhalide emulsions are coated. They can be made by dispersing thecolloidal silver or carbon black in an aqueous dispersion of gelatin andcasein. Various wetting and dispersing agents can be used in aiding thedispersions such as sodium alkyl sulfates of 10 to 18 carbon atoms,lower alkyl naphthalene sulfonic acid alkali metal salts wherein thealkyl groups have 1 to 4 carbon atoms, e. g., tri-isopropyl naphthalenesulfonic acid sodium salt, sodium or potassium alkane sulfonic acidsalts having 10 to 18 carbon atoms, etc. Coating may be accomplished byspreading,

has a marked solubility in water at 20 C.) of

natural or synthetic type. Suitable colloids include water-solublecellulose derivatives, e. g., low substituted cellulose ethers, such asmethyl cellu lose, ethyl cellulose, and benzyl cellulose, celluloseesters having solubilizing acid salt groups, e. g., sodium, potassium,and ammonium salts of cellulose acid phthalate, cellulose ether acids,e. g., sodium cellulose glycollate, casein gelatin mixtures,water-soluble synthetic resins, e. g., polyvinyl alcohol, and esters.

A preferred type of water-soluble layer is composed of a macromolecularwater-soluble acetal of a vinyl alcohol polymer with an aldehydecontaining a free sulfonic acid or free carboxylic acid group or analkali metal, ammonium or amine salt of such acids. An elementcontaining this preferred type of water-soluble layer is shown in Fig. 1of the accompanying drawing wherein a base l is provided on each surfacewith a silver halide emulsion layer 2 and 2, a remov- -ablelayer 3 and3' composed of a macromolecular Water-soluble acetal of a vinyl alcoholpolymer with an aldehyde containing a free sulfonic acid or carboxylicacid group, or a water-soluble salt thereof is deposited on'eachemulsion layer and an antihalation layer 4 and 4 composed of gelatin andcasein in the proportion of 10 to 20 parts :of the former per part ofthe latter which has finely-divided carbon uniformly dispersedtherethrough on removable layers 3 and. 3.

V The water-soluble colloids can be coated from an aqueous solution orsolvent mixtures which do not have a deleterious effect on thelight-sensitivity of the emulsion layers. Aqueous solutions containing 5to 45% by weight of a water-soluble alcohol, e. g., ethanol or methanol,and a small amount, e. g., 0.05 to 2% by weight of a wetting agent arepreferred. From 5 to 20 grams of colloid per 100 cc. of solutionconstitutes a practical range. The coating may be applied by any of themethods useful in coating gelatin emulsions on supports includingthosereferred to above.

The invention will be further illustrated but is not intended to belimited by the following examples.

EXAMPLE I A cellulose acetate film base was suitably subbed with gelatinand coated on each side with a gelatin-silver halide emulsion of theX-ray type. Each emulsion surface was coated at 75 F. with ;thefollowing solution:

A dispersion of the following composition was prepared by mixingSolution B with Solution A and then adding Solution C with Vigorousstirring.

Solution A Water cubic centimeters 9100 Casein grams 1000 Sodiumcarbonate (10% aqueous solution) cubic centimeters 340 7 Solution BC'olloidal carbon (particle size 50 mu) grams 1000 Water cubiccentimeters 2000 Sodium dodecyl sulfate (10% solution) do 20 7 SolutionC Gelatin grams 100 Water cubic centimeter 1250 Sodium dodecyl sulfate(10% aqueous solution) do 100 Saponin (5% aqueous solution) do 100 Themixture was coated onto each methyl cellulose layer at about F. to forma layer approximately 30 microns thick. The above coating operationswere carried out in the absence of actinic radiations. The resultinglayer, after drying, had a density greater than 4.0. No visible fog wasproduced after a 20 minute exposure in a normally lighted room buta'slight edge fog developed, e. g., about inch around the periphery ofthe film. The black antihalation layers and the contiguous water-solublecolloid layers were removed easily after a three minute soak in water bygentle swabbing with cotton.

The film element as described above was exposed in the usual manner toX-ray radiations in ordinary room illumination without the use of acassette. The film was processed as follows:

1. Developed for four minutes in a solution made by admixing thefollowing components:

Hydroquinone grams 7.5 p-N-ethyl-aminophenol sulfate do 5.0 Sodiumsulfite (anhydrous) do 60.0 Sodium carbonate (anhydrous) do 50.0Potassium bromide do 15.0 Water ton. liters 1.0 2. Treated for oneminute in a stop bath of the composition Volumes Acetic acid (28%) 1Water 20 3. The outer black layers were then removed in water by gentleswabbing.

4. Fixed for five minutes in a solution of the composition:

Sodium thiosulfate crystals grams 240.0 Sodium sulfite (anhydrous) do6.0 Boric acid do 6.0 Potassium alum do 12.0 Acetic acid (28%) oubiccentimeters 35.0 Water to liters 1.0

A photographic paper composed of an interfelted white paper stock and ablack pigmented paper stock forming a photographically'opaque blackouter stratum is provided with a baryta Casein g rams 20.0 Water. cubiccentimeters 100.0 NM2CO3 (20%) d0 6.8 Gelatin grams 1.0 Mannitanmonolaurate 10 cubic centimeters.-- 5.0 Water do 50.0

On the surface of the casein gelatin layer was coated a thin layer (e.g., 10 mu.) from a dispersion made by mixing thev following solutionswith stirring.

Solution A Water cubic centimeters 10,000 Casein grams 2,000 Sodiumcarbonate aqueous solution) cubic centimeters 680 Solution B orColloidal carbon (particle size 60 mu) grams 600 ater cubic centimeters3000 Condensationproduct of ethylol cyanamide 'with lauric acid (1%solution) do 2 Solution 0 Gelatin grams 100 Water cubic centimeters 3000Sodium dodecyl sulfate (10% solution-- aqueous) do 25 Saponin (5%solution-aqueous) do 75 Solution B was added to Solution A slowly andthen Solution C was added and the resulting solution filtered. Thecomposition was then 40 coated in darkness onto each of the emulsionlayers of aforesaid film element to a thickness of microns, Theresulting element had a density of greater than 4 on either side. Thelayer was easilyremoved in the developing solu- 5 tion by a gentleswabbing with cotton. The element can be safely handled in daylight orunder ordinary artificial illumination without exposure of thelight-sensitive stratum. Upon exposure and development as in Example Ithe outer layerswere readily removed without leaving any residualdeposit of the light-blocking layer on the film.

EXAMPLE III In place of the methyl cellulose solution of Example I wasused the following:

Corn dextrine grams 10 Water cubic centimeters 100 Ethanol do 20 Saponinsolution do 10 Aerosol CEL (10%) do 2 The resulting element hadproperties similar to those of Example I.

EXAMPLE IV In place of the gelatin-casein coating solution of Example IIwas substituted:

Cellulose acetate-acid phthalate grams 5 10% NazCOa oubic centimeters 10Water do 150 Ethanol do 50 Gelatin grams 5 Water -cubic centimeters- 100r groups.

The resulting element had: properties similar to those of Example I.

ExAMrLE V In place of the gelatin-casein coating solution of Example IIthere was substituted the following solution:

Sodium-o-sulfobenzaldehyde acetal of poly- The resulting completeelement when processed after the manner described in Example I gavesimilar results.

"The hydrophilic macromolecular acetal described in Example V can bemade by the reacti. n-of atvinyl alcohol polymer, including interpolymers, with an aldehyde containing a sulfonic acid or carboxylic acidgroup or an alkali metal, annnonium, or amine-salt of such acids, underacetal-forming conditions. For example, the acetalization may beconveniently carried out in solution or suspension in water or anorganic solvent or diluent using a catalyst such as phosphoric acid,sulfuric acid, hydrochloric acid, etc. Suitable procedures and aldehydes'are described in United States Patent 2,310,943 and in German PatentNo. 643,650. The free acid groups can be converted into salt groups by asimple neutralization.

Partially and completely hydrolyzed polyvinyl alcoholscf low,intermediate, and high viscosity, having a, molecular weight of 5,000 to50,000 and hydrolyzed interpolymers of vinyl esters with one or lessequivalent of a terminally unsaturated interpolymerizable organiccompounds can be used, in preparing, the vinyl alcohol acetals ofaldehydes containing carboxylic or sulfonic acid Y In general, suchpolymer having for each 100 carbon atoms between 20, and 5.0 freenon-phenolic hydroxyl groups are useful.

'Water-soluble, macromolecular, neutralized acetals of vinyl alcoholpolymers useful in accordance with this invention are prepared byacetalizationirom (1) polyvinyl alcohol of high molecular weight(viscosity of 4% aqeuous solution at 20 C., 40 to 60 centipoises) (2)polyvinyl alcohol of medium molecular weight (viscosity of 4% aqueoussolution at 20 C., 15 to 30 centipoises) which may be substituted on 40to 60% of the hydroxyl groups with acetate, propionate,

acetal, propional, and butyral groups, and (3) to hydrolyzedinterpolymers of vinyl acetate with 0.05 to 0.5 mol equivalents ofterminally unsaturated mono-oleflns, e. g., ethylene, such as describedin Roland United States Patent No. 2,386,347, and (4) completelyhydrolyzed interpolymers of vinyl acetate with minor portions (less than50%) 0f polymerizable vinyl or vinylidene compounds, for example, vinylchloride, Vinyl cyanide, alkyl methacrylates, e. g., methyl and ethylmethacrylate, etc., with an aldehyde containing carboxylic or a sulfonicacid group.

The preferred polyvinyl acetals have the above properties and, inaddition, are colorless or substantially colorless and are free fromcolor former nuclei. The preparation of suitable such acetals for theremovable layers is also more fully described in copending applicationSerial No. 651,996 filed March 5, 1946.

Various commercial forms of colloidal carbon or carbon black which havea very fine particle size, for instance, from 10 to 100 millimicrons,including mixtures Of particles having sizes within these ranges can besubstituted for those de scribed in the above examples. Small amounts(e. g., 0.5 to 2% of the gelatin) of the cellulose derivatives describedin such patents may also be present. The black inert pigments can beused in a wide range of proportions, e. g., one part by weight ofpigment to 20 parts of combined casein and gelatin to two parts ofpigment to one part of combined gelatin and casein.

Additional useful wetting agents include a1- kali metal ,alkyl sulfatesof 8 to 20 carbon atoms, .e. g., sodium octyl sulfate, sodium tetradecylsulfate, sodium hexadecyl sulfate, ammonium octadecyl sulfate, oleylsulfate, sodium n-hexadecanesulfonic acid, tri-isopropyl-napththalenesulfonic acid, the condensation products of ethylol cyanimides withlauric, stearic, palmitic, etc., acids.

By varying the proportion of casein to the photographic gelatin it ispossible to modify the properties of the light absorptive layerssomewhat. The higher proportions, e. g., 20 to 25, of casein make thelayers removable in a water rinse before development, whereas somewhatlower proportions render the layers soluble in alkaline developersolution. Proportions near the lower limits render the layers removableat the end of normal development with gentle swabbing. Water rinsesafter development remove all traces of the products.

The antihalation elements of this invention as described above have allthe desirable characteristics of a commercially practical element.Their, prepartion does not present any coating difficulties. The twoouter layers are soluble in aqueous treating baths and may be readilyremoved from the film by treatment in such baths. They arephotographically inert and hence do not adversely affect the radiationsensitive layers. The light-blocking pigments are non-diffusing and areuniformly dispersed throughout the combination' colloid layer.

The invention provides a novel X-ray film which can be handled safely indiffused daylight or under ordinary room illumination but yet can beeasily processed to X-ray photographs. They may be processed in ordinaryillumination if so desired. They eliminate the use of cassettes andenable the technicians to exercise much greater latitude and attain morespeed in roentgenology. In addition, the layers are abrasion resistant,have good anti-static properties, are not affected by usual changes inhumidity, and have good aging properties.

'As many widely different embodiments of this invention'can be madewithout departing from the spirit and scope thereof, it is to' beunderstood that the invention is not to be limited except as defined bythe claims.

-What is claimed is:

1. Aphotogr'aphic'elemeht comprising a base, a light-sensitive emulsionlayer, an outer antihalation layer disposed on each side of said basecomposed of casein and gelatin in the proportion of 10 to 20 parts ofthe former per part of the latter, having intimately and uniformlydispersed therethrough finely divided carbon particles and awater-soluble acetal of a vinyl alcohol polymer containing a group takenfrom the class consisting of free sulfonic acid groups, free carboxylicacid groups, and their water-soluble salts intercalated between saidemulsion layer and antihalation layer.

2. A photographic element comprising a base, a light-sensitive emulsionlayer, an outer antihalation layer disposed on each side of said basecomposed of casein and gelatin in the proportion of 10 to 20 parts ofthe former per part of the latter, having intimately and uniformlydispersed therethrough finely divided carbon particles and awater-soluble sodium-o-sulfobenzaldehyde acetal of polyvinyl alcoholintercalated between said emulsion layer and anti-halation layer.

QTISWILLARD MURRAY.

REFERENCES CITED The following references are of record in the file ofthis patent: V

UNITED STATES PATENTS Number Name Date 1,537,939 Dunham May 9, 19251,631,421 Lohofer June 7, 1927 1,942,852 Young Jan. 9, 1934 2,271,234Staud et al Jan. 27, 1942 2,319,080 Nadeau et a1 May 11, 1943 2,379,373Murray June 26, 1945 FOREIGN PATENTS Number Country Date 163,349 GreatBritain May 26, 1921 212,484 Great Britain Mar. 13, 1924 292,990 GreatBritain Jan. 10, 1929 322,007 Great Britain Nov. 28, 1929

